Recently, in the field of information and telecommunications, optical communications infrastructures have been rapidly constructed to allow large amounts of data to be exchanged at high speed using light. To date, fiber-optic networks extending a large distance (several kilometers or more) have been built, such as backbone, metro, and access networks. However, in order to further reduce the delay in the transmission of a large amount of data, it is necessary to employ fiber optics (instead of conventional metallic cables and wires) also for interconnection between devices or components spaced a very short distance apart from each other, such as between communications devices or racks (several to several hundred meters apart) and even between components within a communications equipment or a rack (several to several ten centimeters apart). The following description will be directed to use of fiber optics (or optical wiring) within communications equipment. Routers and switching devices, for example, contain line cards to receive high frequency signals sent through optical fibers over an external network such as an Ethernet network. In these devices, pluralities of such line cards are coupled to a backplane. The input signals to the line cards are transmitted to a switch card through the backplane, processed by the LSI on the switch card, and then returned to the line cards also through the backplane. It should be noted that, currently, the signal (or data) supplied from each line card to the switch card through the backplane is transmitted at a data rate of 300 Gbits/sec or higher. This means that in the case of conventional electrical wiring (using metallic wires), 100 or more wires are required to reduce the propagation loss and thereby achieve such a high data rate transmission; that is, each wire can carry only approximately 1 to 3 Gbits of data per second. Further, these high frequency lines require an equalizer, as well as some measures against reflection and crosstalk between wires. In the case of conventional electrical wiring, if communications systems increase in capacity in the future and hence require a communication equipment capable of processing information at a rate on the order of terabits/sec, the above problems of increased number of wires required for transmission and of crosstalk between the wires will become more serious. On the other hand, connecting between the line cards and the backplane and between the backplane and the switch card by fiber optics for signal transmission will allow transmission of high frequency signals at a data rate of 10 Gbps or higher with reduced loss, reducing the number of wires required for transmission and eliminating the need for the above measures against reflection and crosstalk between the wires. To achieve this, optoelectronic integrated circuit devices are being developed. These optoelectronic integrated circuit devices can be used in a switch card and contain an LSI package having photonic devices mounted therein. The switch card processes high data rate signals collectively received from the above line cards.
Such an optoelectronic integrated circuit device is reported, for example, in “Opto-Electronics Packaging Techniques for Interconnection,” LEOS2003 (Lasers and Electro-Optics Society), volume 1, p. 26-30, Oct., 2003 (Nonpatent Document 1). FIG. 16 shows this optoelectronic integrated circuit device. Referring to the figure, an LSI 162 and photonic devices 12 are mounted on a package substrate 11 having a bump array 18. The LSI 162 is located at the center portion of the substrate 11, and the photonic devices 12 are disposed along the four sides of the LSI 162. Fiber connectors 15 are directly connected to these photonic devices 12 to achieve an optical coupling. Thus, the optical interconnection paths (or optical wiring) extend close to the LSI 162, which allows high frequency electrical lines 24 connected between the I/O terminals of the LSI 162 and the photonic devices 12 to have a relatively small length, resulting in a reduction in the propagation loss (or transmission loss) of the high frequency signals. This configuration also allows the integration density of the package to be enhanced, since the photonic devices 12 are disposed on the same package substrate 11 as the LSI 162 such that they are located along the four sides of the LSI 162 as described above.
Nonpatent Document 1: “Opto-Electronics Packaging Techniques for Interconnection,” LEOS2003.(Lasers and Electro-Optics Society), volume 1, p. 26-30, Oct., 2003